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Sealed System
Charging The System
Check the serial plate for the correct refrigerant
type. It is extremely important to verify the type of
refrigerant in the system before starting any sealed
system repairs. After charging the system with
liquid, be certain to wait at least 5 minutes before
starting the compressor to give the refrigerant
a chance to disperse throughout the system.
Otherwise the compressor could be damaged by
attempting to pump excessive quantities of liquid.
Preparing The Charging Cylinder:
1.
Charging cylinder must have at least eight (8) ounc-
es more refrigerant than required charge.
2.
Plug in cylinder heater and bring pressure up 30
pounds above gauge pressure at ambient
temperature.
DO NOT USE EXTERNAL HEAT SOURCE ON
CYLINDER OR EXCEED MAXIMUM GAUGE
PRESSURE ON CHARGING CYLINDER.
To charge the system:
1.
Make certain that hand shut-off valve to vacuum
pump is closed.
2.
Close high-side manifold gauge valve.
3.
Set charging cylinder scale to pressure indicated on
cylinder pressure gauge.
4.
Observe refrigerant level in sight glass. Subtract
amount to be charged into system and note shut off
point.
5.
Open charging cylinder valve slowly and allow
proper charge to enter system.
6.
As soon as refrigerant in sight glass has gone down
to predetermined level, close charging cylinder valve.
Disconnect charging cylinder heater at this time
to prevent cylinder pressure from exceeding its
maximum limits.
7.
Allow system to sit for five minutes.
8.
Turn on refrigerator compressor. Run compressor
for a few minutes and monitor system pressures.
6.
When satisfied unit is operating correctly, clamp
the process tube with pinch-off tool with the unit
still running. Using a tubing cutter, cut the process
tube about 2 inches from the pinch-off tool. Use
Sil-fos solder and solder process tube closed.
7.
Turn off the product and allow the unit to set for
a few minutes. Check the process tube for
refrigerant leaks.
Final Leak Test
1.
With the refrigerator turned OFF leak test all
low-side system components.
2.
Turn the unit ON and run until the condenser is
warm. Leak test the high-side system components.
Dedicated Equipment
R-134a must not be mixed with other types of
refrigerants. R-134a must be recovered in dedicated
and properly identified recovery bags and tanks.
It will be necessary to check with the manufacturer of
your recovery equipment to determine R-134a
compatibility. Some recovery equipment manufactur-
ers have changeover instructions for switching between
refrigerant types. Protect yourself and your equipment
by following all manufacturer guidelines.
Also, ensure that your refrigeration hoses are specified
for use with R-134a refrigerant. Research has shown
that compounds in standard refrigeration hoses may
enter sealed systems and ultimately restrict the cap
tube in an R-134a system.
For example, hoses that were used for a refrigeration
system operating on R-12 may contain small quantities
of mineral oil which can block the capillary tube in a
system operating on R-134a. As little as one milligram
may be sufficient to cause a blockage. In addition,
sealed system components that have been used with
CFC systems must not be used with R-134a systems.
These components may contain residual amounts of
refrigerant and oil which could damage an R-134a
system.
At the earliest stage of development work on R-134a,
tests were carried out on a different type of synthetic oil
known as Poly-Alkaline Glycol (PAG). This oil is also
used in certain air conditioning systems for cars. PAG
and Ester oil DO NOT mix with one another. Service
equipment used for R-134a / Ester oil must not come
into contact with PAG.
7-24
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